title: Endothelial Progenitors Exist within the Kidney and Lung Mesenchyme.
abstract: The renal endothelium has been debated as arising from resident hemangioblast precursors that transdifferentiate from the nephrogenic mesenchyme (vasculogenesis) and/or from invading vessels (angiogenesis). While the Foxd1-positive renal cortical stroma has been shown to differentiate into cells that support the vasculature in the kidney (including vascular smooth muscle and pericytes) it has not been considered as a source of endothelial cell progenitors. In addition, it is unclear if Foxd1-positive mesenchymal cells in other organs such as the lung have the potential to form endothelium. This study examines the potential for Foxd1-positive cells of the kidney and lung to give rise to endothelial progenitors. We utilized immunofluorescence (IF) and fluorescence-activated cell sorting (FACS) to co-label Foxd1-expressing cells (including permanently lineage-tagged cells) with endothelial markers in embryonic and postnatal mice. We also cultured FACsorted Foxd1-positive cells, performed in vitro endothelial cell tubulogenesis assays and examined for endocytosis of acetylated low-density lipoprotein (Ac-LDL), a functional assay for endothelial cells. Immunofluorescence and FACS revealed that a subset of Foxd1-positive cells from kidney and lung co-expressed endothelial cell markers throughout embryogenesis. In vitro, cultured embryonic Foxd1-positive cells were able to differentiate into tubular networks that expressed endothelial cell markers and were able to endocytose Ac-LDL. IF and FACS in both the kidney and lung revealed that lineage-tagged Foxd1-positive cells gave rise to a significant portion of the endothelium in postnatal mice. In the kidney, the stromal-derived cells gave rise to a portion of the peritubular capillary endothelium, but not of the glomerular or large vessel endothelium. These findings reveal the heterogeneity of endothelial cell lineages; moreover, Foxd1-positive mesenchymal cells of the developing kidney and lung are a source of endothelial progenitors that are likely critical to patterning the vasculature.
authors.affiliation: Rangos Research Center, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America ; Division of Nephrology, Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Sunder
authors.initials: S
authors.lastname: Sims-Lucas
authors.forename: Caitlin
authors.initials: C
authors.lastname: Schaefer
authors.forename: Daniel
authors.initials: D
authors.lastname: Bushnell
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Ho
authors.forename: Alison
authors.initials: A
authors.lastname: Logar
authors.forename: Edward
authors.initials: E
authors.lastname: Prochownik
authors.forename: George
authors.initials: G
authors.lastname: Gittes
authors.forename: Carlton M
authors.initials: CM
authors.lastname: Bates
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation; D002469:Cell Separation; D066026:Endothelial Progenitor Cells / Q000166:cytology* / Q000378:metabolism; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000378:metabolism; D007150:Immunohistochemistry; D007668:Kidney / Q000166:cytology* / Q000378:metabolism; D008168:Lung / Q000166:cytology* / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology* / Q000378:metabolism; D051379:Mice
chemical_list: D015415:Biomarkers; D051858:Forkhead Transcription Factors; C489562:Foxd1 protein, mouse